1. Field of the Invention
This invention relates to real-time measurement and calculation of a fluorescence lifetime.
2. Description of Related Art
Fluorescence lifetime measurement has become a significant analytical tool with clinical applications (U.S. Pat. No. 7,127,282), research applications (U.S. Pat. No. 7,183,066), and process control applications (U.S. Pat. No. 6,890,485). In all of these applications changes in the analyte are detected as changes in the measured fluorescence lifetime.
Three types of experimental methods are used in measuring fluorescent lifetimes; time correlated single photon counting, multi-phase measurement, and the stroboscopic method. (Lakowicz 1991). All of these methods can output a fluorescence decay curve. That curve is a convolution of the instrumental response function and the analyte fluorescence decay. U.S. Pat. No. 5,039,219 provides details of the stroboscopic measurement method.
U.S. Pat. No. 4,855,930, “Method and apparatus for improved time-resolved fluorescence spectroscopy” is typical of the state of the art for calculating the fluorescence lifetime from the fluorescence decay curve. This method uses convolution/deconvolution with least squares minimization. In practice, the method requires acquiring many time points on the fluorescence decay curve and performing minutes of calculation to calculate a lifetime.